1. Technical Field
The present invention relates generally to vehicle suspension systems and more particularly to a hydraulic anti-roll suspension system for a motor vehicle.
2. Discussion
Traditional vehicle suspension systems include resilient devices, such as coil springs, leaf springs and torsion bars, to flexibly support a portion of a vehicle and enable all of the wheels to maintain contract with the ground when traversing uneven terrain. Segregating the vehicle into unsprung and sprung portions in this manner is also useful for preventing severe impulsive forces from being transmitted to the vehicle occupants. It is known that as a vehicle travels around a corner, centrifugal forces acting on the vehicle tend to cause the sprung portion of the vehicle to roll. In severe instances, the effects of roll could cause instability and impede the ability of the driver to control the vehicle. Although the effects of roll are more pronounced with vehicles having a comparatively high center of gravity, such as vans or trucks, every vehicle is effected by roll.
To combat the effects of roll, anti-roll suspension systems have been developed. Their use, however, has not been widespread, as they have generally proved to be relatively expensive, complex, or inconvenient to manufacture, install or service. For instance, many of these systems require the use of a fluid power source, such as a hydraulic pump, which increases the load on the vehicle""s power source and reduces fuel economy. Furthermore, most anti-roll suspension systems are not easily integrated into vehicles having conventional suspension system components. Consequently, there remains a need for a simplified anti-roll suspension system which is inexpensive and easily integrated into a vehicle equipped with otherwise conventional suspension system components.
It is a general object of the present invention to provide an effective and inexpensive anti-roll suspension system comprised of a pair of double-acting cylinders which are coupled between a sprung portion and an unsprung portion of a vehicle and which are interconnected by a fluid circuit.
It is another object of the present invention to provide an anti-roll suspension system that controls the roll angle of the sprung portion of the vehicle while the vehicle is cornering without decreasing passenger comfort during normal highway conditions.
It is a further object of the present invention to provide an anti-roll suspension system that is easily integrated into a vehicle having conventional suspension components.
In accordance with the present invention, an anti-roll suspension system for a motor vehicle is provided which includes a pair of double-acting cylinders coupling the unsprung and sprung portions of the vehicle. The upper fluid chamber of each cylinder is exclusively connected to the lower fluid chamber of the laterally opposite cylinder to create a fluid circuit having first and second portions which hydraulically interconnect the cylinders. When the vehicle is maneuvered around a corner, the position of the sprung portion rotates relative to the position of the unsprung portion of the vehicle. This relative rotation is resisted by the tendency to substantially equalize the forces acting on the cylinder pistons, thereby reducing the tendency of the sprung portion of the vehicle to roll. As such, anti-roll capabilities are provided without the need for costly fluid pumps which reduce the fuel economy of the vehicle.
In an alternate embodiment, a valve is included which is operable in either of a recirculating mode and a cross-flow mode. When the vehicle is subjected to a centrifugal force which exceeds a predetermined value, the valve is actuated to establish the cross-flow mode and enable fluid to flow between the laterally opposite cylinders. The valve is otherwise maintained in its recirculating mode whereby fluid is circulated between the upper and lower fluid chambers of each individual cylinder. Configuration of the suspension system in this manner controls roll during cornering maneuvers while preventing vertically directed forces encountered by an individual wheel during normal driving conditions from being transmitted to the laterally opposite wheel.
Additional benefits and advantages of the present invention will become apparent to those skilled in the art to which this invention relates from a reading of the subsequent description of the preferred embodiment and the appended claims, taken in conjunction with the accompanying drawings.